Kottelat, M. 2013. The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries. Raffles Bulletin of Zoology Supplement No. 27: 1-663.

Taxonomic Notes:

This species has recently been reviewed by Larson (2010); it is possible that this is a species-complex. A genetic and morphological study covering all habitat types and geographic localities may help to clarify if there are cryptic species within R. bikolanus.

Justification:At present, this widespread species appears to have stable populations in suitable habitat and can be locally common. It is listed as Least Concern. The possibility still exists that there are cryptic species within Redigobius bikolanus; taxonomic work on this remains to be undertaken.

There is some abundance data for populations in northern Queensland (Australia), which show the species to be patchily distributed; it may be common in some streams but less so in others (Pusey et al. 2004). Its highest abundance and density was in the Johnstone River.

Rayner et al. (2008 and 2009), discussed changes in community structure and dietary habits of fishes in the seasonally flooding Mulgrave River, Queensland, finding that the speciesformed a significant part of a gobioid-dominant fish assemblage during the dry season (when flows were lower).

This species is found in fresh and brackish waters, in rivers, small streams, estuaries and mangroves, and has been recorded 120 kilometres upstream in pure freshwater in New Guinea and 160 kilometres upstream in the Fitzroy River, Queensland (Allen 1991, Larson 2010, Pusey et al. 2004). Pusey et al. (2004) give details of habitat/microhabitat types and use for north Queensland rivers, indicating that the species prefers low flow streams, where cover (leaf litter and woody debris) is plentiful. As individuals have been found in lakes and the upper reaches of rivers and above obstructions such as the Fitzroy barrage, it appears that individuals can breed in freshwater. The species has bred in freshwater in captivity (Leggett and Merrick 1987).

There are currently no known major threats to this species. Potential threats include damage to coastal rivers and mangrove habitats through habitat degradation and destruction. Some populations may be more at risk (e.g. Philippines, Singapore) due to development and clearing. The species may be sought after for the aquarium trade.

In Australia this species is listed as Non-threatened (Wager and Jackson 1993), as its preferred habitats are relatively stable and a number of waterways in which it occurs are in protected areas. Further taxonomic work is required as there is a possibility that there are cryptic species within this species.